1. Field of the Invention
This invention generally relates to surgical devices and, in particular, to an apparatus and method for fusing and/or welding tissue.
2. Discussion of Related Art
Surgery generally involves the cutting and fixing of tissue. The cutting is usually undertaken in one of two modalities, either cold cutting or hot cutting. Cold cutting is performed using a mechanical device such as a knife or scissors. Hot cutting involves the use of high frequency electrosurgical current, ultrasonic sound or heat. The fixation of cut tissue commonly involves the use of sutures, staples or clips. More recently, tissue adhesives have evolved as an occasional alternative.
The process of inhibiting blood flow from cut or severed tissue, commonly referred to as hemostasis, is often undertaken using power generated by an electrosurgical device. Various electrosurgical effects can be achieved, such as coagulation, fulguration and cauterization. Coagulation makes use of high frequency electrosurgical waveforms that are designed to desiccate tissue by vaporizing the cellular content and thereby restricting the flow of blood from the site. Fulguration is a form of coagulation that is more broadly applied to provide hemostasis over large areas. Cauterization is a well-known form of hemostasis and has been used for many years. A hot instrument applied to a portion of the severed or damaged tissue will normally arrest blood flow. The application of heat to the tissue fuses the cellular content and actually welds cellular content in a manner somewhat similar to metal welding.
Several procedures have evolved which use devices that provide both cutting and fixation in a single instrument. The most common of these devices comprises a surgical stapler that places two rows of titanium surgical staples and subsequently cuts the tissue between the rows. These devices are often referred to as “take-down” devices. They are used to divide body passages and provide concomitant fluid stasis.
An example of such devices is the commonly available gastro-intestinal anastamosis (GIA) type stapler. It comprises a jaw fitted with a cartridge holding four to six rows of staples in a deployable position, a hinged anvil sized and configured to deform the staples of the cartridge, and a shaft communicating with a handle held by a user. In use, the device is placed along, and compressed upon, a portion of tissue to be cut and stapled. The staples are subsequently urged through the tissue and against the anvil where they are deformed into a preferred folded-over condition. A sharp surgical blade is then moved forward between rows of staples to divide the tissue. Fluid stasis is accomplished by the overlapping rows of folded-over and compressed staples.
As one would imagine, it is not desirable to over-compress tissue or develop a condition where required nourishment to tissue is compromised. If too many staples are placed or if the staples are over-compressed, the included tissue may be deprived of nutrition and may subsequently necrose and cause serious complications. In addition, staples are typically formed of a material which is foreign to the body and may cause responses that will further complicate recovery or healing. Staples cannot be cut through or removed easily. Staples also cause problems with imaging technologies. They may show up as artifacts in MRI, CT scans and fluoroscopy.
Surgical clips are often used to occlude small vessels. They normally comprise a C-shaped metallic member that is highly compressed upon tissue. Nourishment to the residual portion of “clipped-off” tissue is completely interrupted. Even when a divided or repaired portion of tissue is sutured, special care is taken not to place the suture too tightly so that nourishment to the residual portion is interrupted.
Tissue adhesives, which provide hemostasis as well as the “gluing” of tissue, have proven to be effective. However, they often require prior preparation from autologous materials. In addition, they do not have the full confidence of the medical community.
To avoid the complications of clips, staples, adhesives and sutures, attempts have been made to fuse or weld tissue. For instance, a vessel may be clamped tightly with a hemostat or grasper, and subsequently energized with an electrosurgical generator. This technique is commonly referred to as “buzzing the hemostat”. The heat generated within the tissue may cause the proteins of the cellular content to fuse and create a fluid-tight arrangement.
This technique has proved to be relatively effective in small vessels; however, large vessels are not indicated for this approach. The relationship between the diameter of the vessel and the wall thickness has proven to be the limiting factor in tissue fusion and welding in most cases. Hemostatic graspers are available that compress tissue and apply an electrosurgical discharge that mimics the energized hemostat.
An electrosurgical generator is to supply a high voltage at a high frequency in order to produce an electric arc between an electrosurgical instrument and grounded tissue. This “electrosurgical effect” (ESE) is especially suited to cut and coagulate tissue in a quick and effective manner. However, the ESE is not effective to divide and provide hemostasis or fluid stasis in large vessels or conduits. While the ESE has been well adapted to seal small capillaries, it has not been effective to shut-off the fluid flow in a large conduit.